1. Field of the Invention
The present invention relates to a removable pressure sensitive adhesive composition which mainly contains an acrylic polymer and is used in labels, pressure sensitive adhesive tapes or sheets, as well as to such a removable pressure sensitive adhesive sheet using the removable pressure sensitive adhesive composition.
2. Description of the Related Art
Removable (removing type) pressure sensitive adhesives are formed into sheets or tapes and are affixed to surfaces of adherends upon use and are peeled off and removed from the adherends after the intended purpose has been achieved. They are used as pressure sensitive adhesives in pressure sensitive adhesive sheets such as surface protecting films, masking tapes for painting and removable memo pads (e.g., sticky notes).
For example, the surface protecting films are affixed to surfaces of adherends such as a stainless steel sheets, aluminium sheets, prepainted copper sheets, and other metal sheets or plywood to thereby prevent the surfaces of the adherends from staining or damaging upon their transportation, storage or processing. The surface protecting films of this type must adhere to the adherends without peeling off upon their transportation, storage or processing and must easily be removed from the adherends when the films become unnecessary after protection of the adherends.
However, conventional pressure sensitive adhesive tapes often increase in their adhesive strength due to changes with time after adhesion to adherends, and cannot significantly be peeled off from the adherends after adhesion or may leave the pressure sensitive adhesives as deposits and thereby stain the adherends.
As is described above, conventional removable pressure sensitive adhesives become less removable with their increasing tackiness (adhesive strength) with time and thereby cannot significantly be peeled off from the adherends or stain the adherends. For example, the pressure sensitive adhesives may cause adhesive deposits on the adherends. Demands have therefore been made to solve these problems.